CHRONIC MYELOID

LEUKEMIA

By : SHASHIDHARA and SHASHIKUMAR

HEMATOPIESIS

LEUKEMIA

INTRODUCTION

• Malignant disorders of the haematopoietic stem cell compartment, characteristically associated with increased numbers of white blood cells in the bone marrow and/or peripheral blood

• Incidence is 10/100000 per annum. Males are affected more frequently than females (acute leukemia 3:2, chronic lymphocytic leukemia 2:1, chronic myeloid leukemia 1.3:1)

• Acute leukemia occurs at all ages, chronic leukemia occur mainly in middle and old age

HISTORY

• The discovery of leukemia is largely contributed to German physician Rudolf Ludwig Karl Virchow (1821-1902) and

• English physician, pathologist and physiologist John Hughes Bennett (1812-1875) as they were the first to observe the disease

• In 1845 Edinburgh pathologist Bennett reported a “case of hypertrophy of the spleen and liver in which death took place from suppuration of the blood” in the Edinburgh medical journal.

• Few weeks later Virchow in berlin published a very similar case.

• Bennett thought that the patient had an infection, Virchow suspected a neoplastic disorder that he soon called white blood disease or leukemia

CLASSIFICATION

Myeloid neoplasms

Lymphoid neoplasms

Histiocytic neoplasms

MYELOID NEOPLASMS• Includes neoplasms of myeloid cell lineage• There are 5 categoriesMyeloproliferative disordersMyeloproliferative/myelodysplastic diseasesMyelodysplastic syndromes (MDS)Acute myeloid leukemiaAcute biphenotypic leukemia

LYMPHOID NEOPLASMS• Leukemias of lymphoid lineage and lymphomas of B, T or NK cell

origin

• Includes B cell neoplasms ( including plasma cell disorders), T cell neoplasms, NK cell neoplasms and Hodgkin’s disease

HISTIOCYTIC NEOPLASMS• Neoplastic proliferations of histiocytes in Langerhans cell

histiocytisis

CONTD….

• In acute leukemia there is proliferation of primitive stem cells leading to an accumulation of blasts, predominantly in the bone marrow, which causes bone marrow failure

• In chronic leukemia the malignant clone is able to differentiate, resulting in an accumulation of more mature cells

• Lymphocytic and lymphoblastic cells are derived from the lymphoid stem cell (B cells and T cells)

• Myeloid refers to the other lineage, i.e. precursors of red cells, granulocytes, monocytes and platelets

MYELOPROLIFERATIVE DISORDERS

DEFINITION

They are a group of clonal myeloid neoplasms in which a genetic alteration occurs in a hematopoietic progenitor cell leading to its proliferation resulting in an increase in the peripheral blood white blood cells (WBCs), red blood cells (RBCs), platelets, or a combination of these cells.

National Cancer Institute

GeneticMutation

GENETIC MUTATION

CLASSIFICATION

• Chronic myeloid leukemia• Polycythemia vera• Essential thrombocythaemia• Primary myelofibrosis• Systemic mastocytosis• Chronic eosinophilic leukemia• Stem cell leukemia

COMMON FEATURES

• Common pathologic feature of the myeloproliferative disorder is the presence of mutated, constitutively activated tyrosine kinases

• Hematopoietic growth factors act on normal progenitors by binding to surface receptors and activating tyrosine kinases, which turn on pathways that promote growth and survival

• Then mutated tyrosine kinase circumvent normal controls and lead to the growth factor-independent proliferation and survival of marrow progenitors

• Most myeloproliferative disorders originate from multipotent myeloid progenitors

CONTD…

• Increased proliferative drive in the bone marrow• Homing of the neoplastic stem cells to secondary

hematopoietic organs, producing extramedullary hematopoiesis

• Variable transformation to a spent phase characterized by marrow fibrosis and peripheral blood cytopenias

• Variable transformation to acute leukemia

CONTD…

• The diagnosis of leukemia is usually suspected from an abnormal blood count, often a raised white count, and is confirmed by examination of the bone marrow

• This includes the morphology of the abnormal cells, analysis of cell surface markers (immunophenotyping), clone specific chromosome abnormalities and molecular changes

• The features in the bone marrow not only provide an accurate diagnosis but also give valuable prognostic information

CHRONIC MYELOID LEUKEMIA

DEFINITION

A clonal expansion of a hematopoietic stem cell possessing a reciprocal translocation between chromosome 9 and 22 resulting in head to tail fusion of the breakpoint cluster region (BCR) gene on chromosome 22q11 with ABL1 (named after Abelson murine virus) gene located on chromosome 9q34

INTRODUCTION

• Chronic myeloid leukemia (CML) accounts for about 14% of all leukemia

• It is one of the family of myeloproliferative neoplasms (MPNs)

• Almost exclusively a disease of adults with the peak of presentation between 40-60

• Philadelphia chromosome demonstrated cytogenetically(95%) or molecularly(5%)

• Slowly progressive

HISTORY• The Philadelphia cytogenecists Peter Nowel and David Hungerford discovered an abnormally small G-group chromosome that we now call the Philadelphia chromosome (Ph)

• 13yrs later Janet Rowley recognized that Ph was the product of a reciprocal translocation between chromosome 9 and 22

• In 1980s the translocation partners were identified as BCR and ABL, followed by the discovery that unregulated tyrosine kinase activity is critical to BCR-ABL’s ability to transform cells

EPIDEMIOLOGY

• Incidence0.2 to 2.0 per 100000 people per year

• GenderHigher in men than in women (1.3:1)

• AgeIncidence increases slowly with age until the middle

forties there after rises rapidly Median age is 66yr

CONTD…

• Geographic and/or ethnic variations might contribute to the variability of incidences

• Most of the patients who get admitted medical therapy studies are 50 to 60yr (median approximately 53yr)

• Patients in bone marrow transplantation studies are even younger (median age approximately 40yr)

RISK FACTORS

• IONISING RADIATIONRadiotherapy

Atomic bombing

X-ray

• CYTOTOXIC DRUGSAlkylating agents

Exposure to benzene

• GENETIC

identical twin of patients

down’s syndrome

• IMMUNOLOGICAL immune deficiency states

ETIOLOGY

• CML was the first malignancy to be linked to a clear genetic abnormality

• Approximately 95% of the patients with CML have a chromosome abnormality known as the Philadelphia (Ph) chromosome

• This is a shortened chromosome 22 resulting from a reciprocal translocation of material with chromosome 9

• The break on chromosome 22 occurs at breakpoint cluster region (BCR)

• The fragment from chromosome 9 carries the abl oncogene which forms a chimeric gene with the remains of the BCR

CONTD…

• This BCR ABL chimeric gene codes for a 210kDa protein with tyrosine kinase activity

• The chimeric gene is transcribed into a hybrid BCR-ABL1 mRNA in which exon 1 of ABL1 is replaced by variable numbers of 5’ BCR exons

• Bcr-Abl fusion proteins p210BCR-ABL1 are produced that contain NH2-terminal domains of Bcr and COOH-terminal domains of Abl

• A rare breakpoint occurring within 3’ region of the BCR gene yields a fusion protein of 230 kDa, p230BCR-ABL1

• Bcr-abl fusion protiens can transform hematopoietic progenitor cells in vitro

CONTD…

Attachment of the BCR sequences to ABL1 results in 3 critical functional changes Abl protein becomes constitutively active as a tyrosine

kinase (TK) enzyme, activating downstream kinases that prevent apoptosis

The DNA-protein-binding activity of Abl is attenuated; andThe binding of Abl to cytoskeletal actin microfilaments is

enhanced

CONTD..

• Chromosomal instability of the malignant clone is a basic feature of CML

• Heterogeneous structural alterations of the TP53 gene, as well as structural alterations and lack of protein production of the retinoblastoma 1 (RB1) gene and the catalytic component of telomerase, is associated with disease progression

• Rare patients show alterations in the rat sarcoma viral oncogene homologue (RAS)

CONTD…

• Sporadic reports also document presence of an altered v-mync myelocytomatosis viral oncogene homologue (MYC) gene

• Progressive de novo DNA methylation at BCR-ABL1 locus and hypomethylation of the LINE-1 retrotransposon promoter promotes blastic transformation

• Interleukin 1β may be involved in the progression of CML to the blastic phase

• Functional inactivation of the tumour suppressor protein phosphatase A2

CLINICAL FEATURES

SYMPTOMS

• Insidious in onset, some are asymptomatic others may present with fatigue, malaise and weight loss or have symptoms resulting from splenic enlargement, such as early satiety and left upper quadrant pain or mass

• Less common features related to granulocyte or platelet dysfunction are infection, thrombosis or bleeding

• Occasionally leukostatic manifestations due to severe leukocytosis or thrombosis such as vasoocclusive disease, CVA, MI, venous thrombosis, priapism, visual disturbances, pulmonary insufficiency

SYMPTOMS AT PRESENTATION

Symptom Present (%)

TirednessWeight loss

BreathlessnessAbdominal pain and discomfort

LethargyAnorexiaSweating

Abdominal fullnessBruising

Vague ill health

372621211312111077

PROGRESSION OF CML

Characterised by worsening of symptoms• Unexplained fever• Significant weight loss• Increasing dose requirements• Bone and joint pain• Bleeding, thrombosis and infection

Less than 10-15% of newly diagnosed patients present with accelerated disease or with de novo blastic phase CML

SIGNS

• Minimal to moderate spenomegaly• Mild hepatomegaly• Persistent splenomegaly despite continued medication is a sign of disease acceleration

• Lymphadenopathy and myeloid sarcomas are unusual

CHRONIC PHASE

• Approximately 85% of the patients with CML are in this phase at the time of diagnosis

• It is sometimes called the stable phase

• Patients are usually asymptomatic (25 to 60%)

• In symptomatic patients, the most common presenting signs and symptoms are

FatigueLeft upper quadrant pain or massWeight lossPalpable spleen in 30 to 70% of patientsLiver is enlarged in 10 to 20%

CONTD…

• Patients with very high WBC counts may have manifestations of hyperviscosity, including priapism, tinnitus, stupor, visual changes and CVA

• If untreated or treated with drugs that do not significantly affect the Philadelphia- chromosome cells in the marrow, chronic phase is associated with a median survival of 4 to 5 yrs

• In the absence of treatment chronic phase progresses to this phase

ACCELERATED PHASE

• This is an ill-defined transitional phase• The criteria used in all the studies with interferon and

tyrosine kinase inhibitors include the presence of any one of the following factors

CONTD…

• Cytogenetic evolution with new abnormalities in addition to Philadelphia chromosome

• The classification used may affect the expected outcome of a group of patients

• More frequently symptomatic, including fever, night sweats, weight, progressive splenomegaly

• Accelerated phase indicates that the disease is progressing and transformation to blast crisis is imminent

• With imatinib therapy 4 yr survival rate exceeds 50%

BLAST CRISIS

• This is the final phase in the evolution of CML, behaves like an acute leukemia with rapid progression and short survival

• It is diagnosed if any of the following is present > 20% blasts in the marrow or peripheral blood Large clusters of blasts in the bone marrow on biopsy Development of chloroma (solid focus of leukemia

outside the bone marrow- CNS, lymph nodes, skin etc)

CONTD…

• Recent evidence suggests patients with 20 to 29% blasts have a significantly better prognosis than those having at least 30% blasts

• Approximately 70% of these patients have a myeloid phenotype, 25% have a lymphoid phenotype and 5% have an undifferentiated phenotype

• Symptoms include weight loss, fever, night sweats, bone pain

• Anemia, infectious complications and bleeding are common

CONTD…

• Subcutaneous nodules or hemorrhagic tender skin lesions, lymphadenopathy and signs of CNS leukemia may be present

• Patients in blastic phase usually die within 3 to 6 months

• Prognosis is slightly better in lymphoid blastic phase

HEMATOLOGICAL FINDINGS

• Elevated white blood cell count with increase in both immature and mature granulocytes

• <5% circulating blasts and <10% blasts and promyelocytes with majority of cells being myelocytes, metamyelocytes and band forms

• Elevated platelet counts• Mild degree of normocytic normochromic anemia• Leukocyte alkaline phosphatase is low in CML cells• Basophilia resulting in production of Histamine

• Bone marrow cellularity is increased with increased myeloid-to-erythroid ratio

• Marrow blast percentage may be normal or slightly elevated

• Marrow or blood basophilia, eosinophilia, and monocytosis

• Collagen fibrosis in the marrow is unusual but reticulin stain-measured fibrosis are noted in half of the patients

DISEASE ACCELERATION

• Increasing degree of anemia unaccounted for by bleeding• Cytogenitic clonal evolution• Blood or marrow blasts between 10 and 20%• Blood or marrow basophils ≥ 20%• Platelet count <100000/µl

• Blast crisis is defined as acute leukemia with blood or marrow blasts ≥ 20%

• Hypopigmented neutrophils may appear (pelger-huet anomaly)

• Blast cells can be classified as myeloid, lymphoid, erythroid, or undifferentiated based on morphologic, cytochemical and immunologic features

PELGER HUET ANOMALY

CHROMOSOMAL FINDINGS

• Hallmark of CML is t(9;22) found in 90-95% of the patients• Shortened chromosome 22 designated as the Philadelphia chromosome that arises from the reciprocal t(9;22)

• Some have complex translocations- variant translocations involving 3,4,5 chromosomes

• Investigations that can be done are karyotyping, fluorescence in-situ hybridization (FISH), quantitative RT-PCR

KARYOTYPING

Bcr- Ch 22

Abl – Ch 9

Bcr-Abl Fusion

FISH

MANAGEMENT

LABORATORY FINDINGS

I. Blood picture:

a. Anemia- usually of moderate degree and is normocytic normochromic in type. Occasional normoblasts may be present.

b. White blood cells-

Marked leucocytosis ( approximately 2,00,000/µl or more at the time of presentation )

The natural history of CML consists of 3 phases-chronic, accelerated and blastic.

Chronic phase

- begins as a myeloproliferative disorder and consists of excessive proliferation of myeloid cells ( mainly myelocytes and metamyelocytes ) and mature segmented neutrophils.

-Myeloblasts usually do not exceed 10% of cells in the peripheral blood and bone marrow.

-Increase in basophils upto 10% is a characteristic feature of CML.

- A rising basophilia is indicative of impending blastic transformation.

Accelerated phase

-There is progressively rising leucocytosis

-Associated with thrombocytosis or thrombocytopenia and spleenomegaly

-Increasing degree of anemia

-Blast count in blood or marrow is b/w 10-20%

-Marrow basophils 20% or more

Blastic phase or blast crisis

-It resembles the acute leukemia in having blood or marrow blasts > or =20%.

-These blasts cells may be myeloid, lymphoid, erythroid or undifferentiated and are established by morphology, cytochemistry or immunophenotyping.

-Myeloid blast crisis is more common and resembles AML

-However, unlike AML, Auer rods are not seen

c. Platelets

-count may be normal but is raised in about half the cases

(2) Bone marrow examination

examination of marrow aspiration yields the following results Cellularity

-there is hypercellularity with total or partial replacement of fat spaces by proliferating myeloid cells. Myeloid cells

-they predominate in the bone marrow with ↑sed M:E ratio

-The differential counts of myeloid cells in the marrow show similar findings as seen in the peripheral blood with predominance of myelocytes

Erythropoiesis

-Is normoblastic but there is reduction in erythropoietic cells Megakaryocytes

-are conspicuous but are usually smaller in size than normal Cytogenetic studies on blood and bone marrow cells

show the characteristic chromosomal abnormality called the philadelphia (Ph) chromosome seen in 90-95 % cases of CML.

- is identified by microsatellite PCR/ by FISH

NORMAL ADULT BONE MARROW COUNTS

• Fat /cell ratio: 50:50

• Myeloid / Erythroid ratio: 2 to 4 : 1( mean 3:1)

• Myeloid series : 30-45%

• Erythroid series : 10-15%

• Myeloblasts : 0.1- 3.5%

• Promyelocytes: 0.5-5%

• Megakaryocytes : 0.5%

• Lymphocytes : 5-20%

• Reticulocytes : 0.1-2%

(3) Cytochemistry

- The only significant finding on cytochemical stains is reduced scores of neutrophil alkaline phosphatase (NAP) which helps to distinguish CML from myeloid leukaemoid reaction

-Leukaemoid reaction is defined as a reactive excessive leucocytosis in the peripheral blood resembling that of leukemia in a patient who does not have leukaemia. Here NAP is increased.

• (4) Other investigations➔ Elevated serum vitamin B12 and vitamin B12 binding

capacity- is due to ↑ in the transcobalamin present in neutrophil granules

➔ Elevated serum uric acid levels➔ Elevated serum LDH➔ Blood sugar may be falsely reduced due to glucose

uptake and metabolism by leucocytes

TREATMENT• Pathophysiology of CML:● The t(9,22) involves fusion of BCR(breakpoint cluster

region) gene on chr 22q11 with ABL(abelson murine leukaemia virus) gene located on chr 9q34.

● The fusion product so formed is termed “Ph chromosome t(9,22)(q34;11),BCR/ABL”

● This brings about the following functional changes● -ABL protein is activated to function as a tyrosine

kinase that in turn activates the other kinases which inhibits apoptosis

-Ability of ABL to act as DNA binding protein is altered

-Binding of ABL to actin of the cytoskeleton is increased

Exact mechanism of progression of CML to the blastic phase is not known. But following mechanisms may be responsible

-structural alterations in p53 and Rb gene

-alterations in RAS and MYC oncogenes

TREATMENT

• A) Treatment of chronic phase

• 1. Imatinib

MOA- competitively inhibits the ATP binding site of the ABL kinase and thus promotes the apoptosis in BCR/ABL +ve cells and thus eliminates them

It reduces the uncontrolled proliferation of white cells

Recommended as 1st line therapy in chronic phase

Produces complete cytogenetic response[ disappearance of Ph chromosome ] in 76% cases at 18 months of therapy

Patients are monitered by repeated bone marrow examination until a complete cytogenetic response, and then by 3 monthly microsatellite PCR/ by FISH

Side effects: fluid retention, nausea, muscle cramps, diarrhoea, skin rash, myelosuppression

Resistance to imatinib results from over expression of BCR-ABL gene or genetic alteration

If a patient fails to respond to imatinib then

2nd generation tyrosine kinase inhibitors{ dasatinib and nilotinib } can be used

or

Allogenic bone marrow transplantation

or

Classical cytotoxic drugs such as hydroxyurea(hydroxy carbamide), melphalan, busulphan

or

Interferon

2. ALLOGENIC B.M TRANSPLANTATION

● Indicated in patients <35 years who have a suitable donor

● Best results are obtained when the transplantation is done in early chronic stable phase

● It can result in permanent disappearance of philadelphia chromosome +ve clone and hence can cure CML in early stages

Procedure:

- healthy marrow or blood stem cells from a donor are infused I.V. Into the recipient, who has been suitably 'conditioned'.

-The conditioning treatment (chemotherapy with or without radiotherapy) destroys the malignant cells and immunosuppresses the recipient, as well as ablating the recipient's haematopoietic tissues

-The injected donor cells home to the marrow engraft and produce enough erythrocytes, granulocytes and platelets for the patient's needs after about 3-4 weeks

-During this period of aplasia patients are at risk of infection and bleeding, and require intensive supportive care

-It may take several years to regain normal immunological function

-ADVANTAGE: is that the donor's immunological system can recognise the residual malignant recipient cells and destroy them. This can be boosted post-transplantation by the infusion of T cells taken from the donor, so called donor lymphocyte infusion(DLI)

Complications :

-mucositis -secondary malignant

-infection disease

-bleeding

-cataract formation

-pneumonitis

-infertility

-graft v/s host disease

3. CYTOTOXIC DRUGS

● Hydroxy urea was previously used widely for initial control of disease, and is still useful in this this context or in palliative situations.

● It does not diminish the frequency of the Ph chr or affect the onset of blast cell transformation.

4. INTERFERON Α-It can induce remission and maintain control in chronic stable phase.

- Not effective in accelerated or blast phase.

-Dose: 3-9 mega units/day i.m or s.c

-may be combined with cytosine arabinoside.

-It brings about:

↓ in bone marrow cellularity

↓ in no. of Ph +ve cells in 20% of cases

Elimination of Ph chromosome in 5% of cases

Reduction of platelet count when it is very high.

• - Adverse effects: flu like syndrome, wt loss, fatigue, nausea, vomiting, headache.

• 5. Others:➔ Splenic irradiation➔ Splenectomy➔ Leucopheresis

•

LEUKAPHERESIS AND SPLENECTOMY

Leukapheresis :

-It may control the blood count in chronic phase CML

-But, expensive and cumbersome

-Useful in emergencies where leukostasis related complications like pulmonary failure or CVA are likely.

-Also useful in pregnant women, in whom it is to avoid potentially teratogenic drugs.

Splenectomy :

-It was used in the past because of the suggestion that evolution to the acute phase might occur in spleen.

-However, this is not the case, and splenectomy is now reserved

a) For symptomatic relief of painful splenomegaly unresponsive to imatinib or chemotherapy.

b) For significant anemia or thrombocytopenia associated with hypersplenism.

Splenic irradiation is used rarely to reduce the size of the spleen.

B) ACCELERATED PHASE

1. Imatinib

2. Hydroxycarbamide ( can be an effective single agent)

3. Low dose cytarabine

C) WHEN BLAST TRANSFORMATION OCCURS

The type of blast cell should be determined

1. If disease is lymphoblastic, treatment is similar to acute leukaemia and response to the treatment is better.

-Aim is to destroy the leukaemic clone of cells without destroying the residual normal stem cell from which repopulation of the haematopoietic tissues will occur.

-there are 3 phases

• Phase 1[Remission induction]→ The bulk of the tumour is destroyed by combination chemotherapy. They require intensive supportive care.

• Phase 2[Remission consolidation]→ This consists of a no. of courses of chemotherapy which attacks the residual disease.

• Phase 3[Remission maintenance]→ consisting of a repeating cycles of drug administration. This may extend for up to 3 years.

• Induction →Daunorubicin, Methotrexate, vincristine, Prednisolone.

• Consolidation→Daunorubicin, Methotrexate, Cytarabine, Etoposide.

• Maintenance→Methotrexate, Vincristine, Prednisolone, Mercaptopurine.

INTENSIVE SUPPORTIVE CARE

Anemia : is treated with red cell concentrate transfusions.

Bleeding :

-Thrombocytopenic bleeding requires platelet transfusions, unless the bleeding is trivial.

-Prophylactic platelet transfusion should be given to maintain the platelet count above 10x10 9/L.

-coagulation abnormalities occur and need accurate diagnosis and treatment as appropriate

Control of infections with appropriate antibiotics Metabolic problems:

-cellular breakdown during chemotherapy releases intracellular ions and nucleic acid breakdown products causing hyperkalaemia, hyperuricaemia, hyperphosphataemia, and hypocalcaemia

-this may cause renal failure

-Allopurinol and I.V. Hydration are given to try to prevent this.

- Prophylactic rasburicase(a recombinant urate oxidase enzyme) can be used.

-occasionally, dialysis may be required.

Psychological problems:

-Delusions, hallucinations are not uncommon.

-patient should be kept informed, and their questions answered and fears allayed as far as possible

-An optimistic attitude from the staff is vital.

COMPLICATIONS

Fatigue : The diseased WBC’S crowd out healthy RBC’S and anemia occurs. This leads to tiredness, easy fatiguability, generalized weakness, lethargy and headache.

• Treatment of CML also can cause a drop in RBC’SExcess bleeding:

• -is due to ↓ in platelet count.

• -epistaxis, bleeding from gums, petechiae Pain : CML can lead to bone pain or joint pain as the bone marrow

expands when excess WBC build up.

Enlarged spleen:- some of the extra blood cells produced in CML are stored in

spleen. - This causes splenomegaly and it takes up space in the abdomen

and makes the patient feel full even after small meals.- Or causes pain in the left upper part of the abdomen. Infections :

• -Although people with CML have too many WBC, these cells are often diseased an don’t function properly.

• -In addition, treatment can cause further ↓ in WBC Thrombosis : is due to leukostasis which may lead to pulmonary

failure and CVA.